The field of the disclosure relates generally to electric machines, and more specifically, to a permanent magnet rotor for use in an electric machine and to methods of assembling such rotors.
Various types of electric machines include permanent magnets. For example, a direct current (DC) motor may include a plurality of permanent magnets coupled to an exterior surface of a rotor core. Typically, the plurality of permanent magnets are coupled to the exterior surface of the rotor core using an adhesive and/or a retaining ring. The plurality of permanent magnets must be coupled to the rotor core such that the permanent magnets remain coupled to the rotor core even when high speed rotation of the rotor exerts forces on the permanent magnets tending to separate the permanent magnets from the rotor core.
Magnets attached to the rotor core with an adhesive are known to have bonding issues. Specifically, magnets have been known to detach from the rotor core during periods of high RPM motor operation. Reliability of magnet retention hinges on strict process control in manufacturing, for example, chemical preparation and application with respect to the rotor core, the magnets, and the adhesive.
In end use applications, environmental factors such as temperatures and humidity as well as other corrosive elements affect integrity of a rotor having magnets attached thereto with an adhesive. It is not uncommon to see bonding failures either at a test facility or in the end use application due to aforementioned factors.